Measurement method, measurement apparatus, camera, and storage medium having stored therein computer program

ABSTRACT

A method includes: acquiring a first level value in a first color area; acquiring a second level value in a second color area; calculating a first corrected level value by adding X% of a difference between the first level value and the second level value to the first level value; calculating a second corrected level value by subtracting Y% of the difference from the second level value; specifying a first corrected level position and a second corrected level position at a boundary between the first color area and the second color area; and measuring a bokeh amount of the image at the boundary between the first color area and the second color area by multiplying the distance between the specified first corrected level position and the specified second corrected level position by 100/(100−X−Y).

CROSS REFERENCE TO RELATED APPLICATION

The disclosure of International Patent Application No. PCT/JP2012/007434filed on Nov. 20, 2012, which claims priority based on Japanese PatentApplication No. 2011-254563 filed on Nov. 22, 2011 is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a measurement method, a measurementapparatus, a camera, and a computer readable recording medium havingstored therein a measurement computer program for measuring a bokeh ofan image.

2. Description of the Background Art

Japanese Laid-Open Patent Publication No. 2008-289122 discloses anevaluation method for an image in which a shaking table holding animaging apparatus is shaken based on a model waveform, a predeterminedobject is imaged by the imaging apparatus with the shaking table beingshaken, and the image taken by the imaging apparatus is evaluated. Here,the model waveform is generated by acquiring a plurality of pieces ofvibration information about a vibration given to the imaging apparatuswhen a photographer takes an image of an object, and then performingstatistic processing for frequency information of all or some of theacquired pieces of vibration information.

Japanese Laid-Open Patent Publication No. 2009-211023 discloses anevaluation method of calculating an evaluation value of the performanceof an image stabilization function of a camera by using an image takenby a camera being shaken, with its image stabilization function beingON.

SUMMARY OF THE INVENTION

The present disclosure provides a measurement method and the like thatcan measure a bokeh of an image with a high accuracy.

In order to achieve the above object, a measurement method of thepresent disclosure includes: acquiring an image signal by imaging anobject with a camera, the object including a first color area composedof a first color, and a second color area which is composed of a secondcolor different from the first color and is adjacent to the first colorarea; acquiring a first level value that is the level value of the imagesignal in the first color area; acquiring a second level value that isthe level value of the image signal in the second color area;calculating a difference between the first level value and the secondlevel value; calculating a first corrected level value by adding X% ofthe calculated difference to the first level value; calculating a secondcorrected level value by subtracting Y% of the calculated differencefrom the second level value; specifying a first corrected level positionand a second corrected level position at a boundary between the firstcolor area and the second color area included in the acquired imagesignal, the first corrected level position being a position where thelevel value of the image signal is the first corrected level value, andthe second corrected level position being a position where the levelvalue of the image signal is the second corrected level value;calculating a distance between the specified first corrected levelposition and the specified second corrected level position; andmeasuring a bokeh amount of the image at the boundary between the firstcolor area and the second color area by multiplying the calculateddistance by 100/(100−X−Y).

Thus, the influence of noise of an image at the boundary between thefirst color area and the second color area can be excluded. Therefore, abokeh amount of an image can be measured with a high accuracy.

Here, a level value indicated by the acquired image signal may benormalized with reference to a specific range, and the normalized levelvalue may be used as the level value of the image signal.

Thus, even if the difference of the level value indicated by theacquired image signal among a plurality of color areas is small, thedifference is enlarged by the normalization. Therefore, a bokeh amountof an image can be measured with a high accuracy.

It is noted that the measurement method of the present disclosure can berealized as a measurement apparatus or a computer program. In addition,the computer program realizing the measurement method of the presentdisclosure can be stored in a storage medium such as an optical disc, amemory card, a magnetic disk, a hard disk, or a magnetic tape.

In addition, the means for realizing the measurement method of thepresent disclosure may be stored in a camera. The means for realizingthe measurement method of the present disclosure may be composed of acomputer program, a wired logic, or the like.

Thus, in a camera, a bokeh amount of a taken image can be measured witha high accuracy.

The present disclosure is effective for measuring a bokeh amount of animage with a high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the configuration of an evaluationsystem;

FIG. 2 is a plane view of a motion blur measurement chart;

FIG. 3 is a block diagram showing the configuration of a camera to bemeasured;

FIG. 4 is a block diagram showing the configuration of a vibratoryapparatus;

FIG. 5 is a graph showing an example of vibration data for a camerahaving a small mass;

FIG. 6 is a graph showing an example of vibration data for a camerahaving a large mass;

FIG. 7 is a flowchart showing a procedure for generating vibration data;

FIG. 8 is a schematic diagram for explaining a procedure for generatingvibration data;

FIG. 9 is a schematic diagram for explaining a generation procedure forvibration data;

FIG. 10 is a block diagram showing the configuration of a computer;

FIG. 11 is a block diagram showing the configuration of motion blurmeasurement software;

FIG. 12 is a block diagram showing the configuration of evaluation valuecalculation software;

FIG. 13 is a flowchart showing the whole evaluation procedure;

FIG. 14 is a flowchart showing an imaging procedure in a static state;

FIG. 15 is a flowchart showing an imaging procedure in a static state;

FIG. 16 is a flowchart showing a camera shake measurement procedure;

FIG. 17 is a schematic diagram for explaining a method of measuringcamera shake;

FIG. 18 is a flowchart showing an evaluation value calculationprocedure;

FIG. 19 is a graph showing the trajectory of a theoretical motion bluramount;

FIG. 20 is a graph showing the relationship among a theoretical motionblur amount, a bokeh offset amount, and an estimated comprehensive bokehamount;

FIG. 21 is a graph showing the trajectories of an estimatedcomprehensive bokeh amount and a measured comprehensive bokeh amount;

FIG. 22 is a graph showing a calculation method for an evaluation valueof an image stabilization performance;

FIG. 23 is a graph showing the trajectory of a bokeh amount forexplaining the influence of a bokeh offset amount;

FIG. 24 is a graph showing the trajectory of a bokeh amount forexplaining the influence of a bokeh offset amount;

FIG. 25 is a graph showing the trajectory of a bokeh amount forexplaining the influence of a bokeh offset amount; and

FIG. 26 is a graph showing the trajectory of a bokeh amount forexplaining the influence of a bokeh offset amount.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments will be described in detail by referring thedrawings as necessary. However, there will be instances in whichdetailed description beyond what is necessary is omitted. For example,detailed description of subject matter that is previously well-known, aswell as redundant description of components that are substantially thesame will in some cases be omitted. This is to prevent the followingdescription from being unnecessarily lengthy, in order to facilitateunderstanding by a person of ordinary skill in the art.

The inventors provide the following description and the accompanyingdrawings in order to allow a person of ordinary skill in the art tosufficiently understand the present disclosure, and the description andthe drawings are not intended to restrict the subject matter of thescope of the patent claims.

Embodiment 1 1. Configuration of Measurement System

FIG. 1 is a block diagram showing the configuration of a measurementsystem according to embodiment 1.

The measurement system according to embodiment 1 is a system formeasuring the performance of an image stabilization function of a camera400 to be measured, by imaging a motion blur measurement chart 300 withthe camera 400 to be measured in the state in which the camera 400 to bemeasured is fixed on a vibratory table 120 of a vibratory apparatus 100,and by analyzing the obtained image by a computer 200 camera 400 to bemeasured.

Here, a camera shake means that a camera moves because a hand holdingthe camera is unstable, resulting in subject shake in a shot image. Inaddition, the image stabilization function refers to a function ofcorrecting a bokeh in an output image caused by the motion of a cameradue to camera shake, by using the output of camera shake detectionmeans. A motion blur amount is an amount corresponding to the movementof an object on a shot image caused by camera shake.

The vibratory apparatus 100 vibrates the vibratory table 120 by a pitchdirection vibrating mechanism 140 and a yaw direction vibratingmechanism 130. The yaw direction vibrating mechanism 130 is a mechanismfor giving a vibration around the X axis in FIG. 1. That is, the yawdirection vibrating mechanism 130 gives the vibratory table 120 avibration simulating a camera shake in the horizontal direction aroundthe vertical axis caused upon imaging by the camera 400 to be measuredin a right posture. The vibration around the X axis is referred to as ayaw direction vibration. In addition, the pitch direction vibratingmechanism 140 is a mechanism for giving a vibration around the Y axis inFIG. 1. That is, the pitch direction vibrating mechanism 140 gives thevibratory table 120 a vibration simulating a camera shake in thevertical direction around the horizontal axis perpendicular to anoptical axis upon imaging by the camera 400 to be measured in a rightposture. The vibration around the Y axis is referred to as a pitchdirection vibration.

The vibratory table 120 can fix the camera 400 to be measured by somemeans. For example, the camera 400 to be measured may be fixed by screwfastening, or may be fixed by an adhesive tape. Any fixing means may beused but it is necessary that the fixing is not easily released when avibration is given to the camera 400 to be measured. The vibratory table120 transmits the vibration given by the yaw direction vibratingmechanism 130 and the pitch direction vibrating mechanism 140, to thecamera 400 to be measured.

A release button pressing mechanism 150 is for pressing a release button471 of the camera 400 to be measured. The release button pressingmechanism 150 may be composed of a solenoid mechanism, for example. Itis noted that in embodiment 1, the release button 471 is mechanicallypressed by the release button pressing mechanism 150, to perform shutterrelease of the camera 400 to be measured. However, the shutter releasemay be performed by another method. For example, the camera 400 to bemeasured itself may perform release by an electric signal beingtransmitted to the camera 400 to be measured via wire or wirelessly.Alternatively, an evaluator may manually press the release button 471.Still alternatively, in the case of mechanically pressing the releasebutton 471 by the release button pressing mechanism 150, a vibration dueto the pressing may be applied to the camera 400 to be measured.

A vibratory controller 110 controls the entire vibratory apparatus 100including the yaw direction vibrating mechanism 130, the pitch directionvibrating mechanism 140, the release button pressing mechanism 150, andthe like.

The computer 200 is, for example, a personal computer, and performstransmission and reception of a signal with the vibratory apparatus 100and the camera 400 to be measured. The computer 200 gives informationabout shutter release or vibration data to the vibratory controller 110,and acquires a shot image from the camera 400 to be measured.Transmission and reception of a signal between the computer 200 and thevibratory apparatus 100 or the camera 400 to be measured may beperformed via wire or wirelessly. In addition, acquisition of a shotimage from the camera 400 to be measured may be performed by wired orwireless communication or via a memory card.

1-1. Motion Blur Measurement Chart

FIG. 2 shows an example of a motion blur measurement chart 300. Themotion blur measurement chart 300 is a chart used as an object to beimaged upon measurement of the image stabilization performance. A blackarea 301 is an area colored in black. A white area 302 is an areacolored in white. An imaging area marker 303 is a marker used as areference for setting an imaging area. The motion blur measurement chart300 is not limited to that shown in FIG. 2 but various types may beapplied thereto. For example, instead of a combination of black andwhite, the motion blur measurement chart 300 may be a pattern composedof several kinds of color areas having chroma. Alternatively, instead ofsuch a geometric pattern, the motion blur measurement chart 300 may be apattern partially including a real picture. In essence, the motion blurmeasurement chart may be a chart including a plurality of color areas.In embodiment 1, a bokeh amount of an image is evaluated by measuring abokeh of the image at the boundary between different color areas of themotion blur measurement chart. Here, color of the color area is aconcept including black, gray, and white which have no chroma and alsoincluding colors having chroma. In addition, a bokeh refers to aphenomenon in which the sharpness of a shot image reduces due todisplacement between the focus plane of a lens and an imaging plane ofan imaging device, camera shake, or the like. The bokeh can occur due toimage processing for image data. A bokeh amount refers to a valueobtained by quantifying the magnitude of a bokeh.

1-2. Example of Camera to be Measured

FIG. 3 is a block diagram showing an exemplary configuration of thecamera to be measured. The camera 400 to be measured generates imagedata by a CCD image sensor 420 taking an object image formed in anoptical system 410.

The optical system 410 includes a zoom lens 411, a mechanical shutter413, a camera shake correcting lens 414, a focus lens 416, and the like.The zoom lens 411 is movable along the optical axis of the opticalsystem 410, and can change the focal length by the movement. A zoommotor 412 drives the zoom lens 411 along the optical axis. Themechanical shutter 413 transmits or shuts off light entering the CCDimage sensor 420 upon imaging, in accordance with control from thecontroller 440. The length of time during which the light is transmittedupon imaging is referred to as a shutter speed or an exposure time. Thecamera shake correcting lens 414 moves on a plane perpendicular to theoptical axis, whereby a subject shake on an image formed on the CCDimage sensor 420 plane can be reduced. Therefore, owing to the camerashake correcting lens 414, the camera 400 to be measured has an imagestabilization function. Here, since the image stabilization function ofthe camera 400 to be measured is realized by the camera shake correctinglens 414, in other words, it can be said that the camera 400 to bemeasured is a camera having an optical image stabilization function ofan inner lens shift type. An actuator 415 drives the camera shakecorrecting lens 414 on a plane perpendicular to the optical axis. Thefocus lens 416 is movable along the optical axis, and can change thefocus state of an object image by the movement. A focus motor 417 drivesthe focus lens 416 along the optical axis.

The CCD image sensor 420 generates image data by taking an object imageformed by the optical system 410. A timing generator 421 transmits asynchronization signal to the CCD image sensor 420 in accordance with aninstruction from the controller 440. By variously changing thesynchronization signal, the operation of the CCD image sensor 420 iscontrolled. An AD converter 430 converts image data generated by the CCDimage sensor 420 from an analog signal to a digital signal.

The controller 440 controls the whole camera 400 to be measured. Thecontroller 440 can be realized by a microcomputer, for example. Inaddition, the controller 440 may be composed of one semiconductor tip ormay be composed of a semiconductor tip for realizing an image processingsection and a semiconductor tip for realizing an operation controlsection.

A card slot 450 allows a memory card 451 to be attached thereto, andperforms transmission and reception of data with the memory card 451. Acommunication section 460 performs transmission and reception of datawith the computer 200. An operation section 470 is composed of a crosskey, a press button, a touch panel, or the like, and is a member formaking various settings of the camera 400 to be measured. The releasebutton 471 is an operation member for giving an instruction for shutterrelease to the controller 440 by a pressing operation from a user.

A gyro sensor 480 is a sensor for measuring an angular velocity. Byfixing the gyro sensor 480 on the camera 400 to be measured, the amountof a vibration given to the camera 400 to be measured can be measured.Based on information from the gyro sensor 480, the controller 440controls the actuator 415 so as to drive the camera shake correctinglens 414 in a direction that cancels the camera shake. Thus, the imagestabilization function of the camera 400 to be measured is realized.

It is noted that the camera 400 to be measured described above is merelyan example of a camera to be measured. Besides the camera 400 to bemeasured, the measurement method according to embodiment 1 can apply tomeasurement of the performance of an image stabilization function ofvarious cameras as long as the camera has an image stabilizationfunction. For example, although the camera 400 to be measured is acamera provided with a zoom lens, a single-focus camera may be used. Inaddition, although the camera 400 to be measured is a camera having anoptical image stabilization function of an inner lens shift type, themeasurement method according to embodiment 1 is also applicable to acamera having an optical image stabilization function of another typesuch as an imaging device shift type, and to a camera having anelectronic image stabilization function instead of the optical imagestabilization function. In addition, although the camera 400 to bemeasured is a camera having a built-in lens unit, a camera withinterchangeable lenses such as a single-lens reflex camera may be used.In this case, instead of evaluation of only a camera itself, a camerasystem including the interchangeable lenses is evaluated. In addition,although the camera 400 to be measured is a camera that performsexposure by a mechanical shutter, a camera that performs exposure by anelectronic shutter may be used. In addition, although in the abovedescription, a simple configuration has been shown as the configurationof the optical system 410 for facilitating the description, the opticalsystem may include more lenses. In essence, any camera to be measuredhaving such an image stabilization function may be used. The measurementmethod according to embodiment 1 mainly uses a still image as anevaluation target. As a matter of course, since a moving image iscollection of still images, also a moving image can be evaluated byevaluating individual still images composing the moving image by themeasurement method according to embodiment 1.

It is noted that, as described above, the measurement method accordingto embodiment 1 is also applicable to a camera having an electronicimage stabilization function. However, there are various types ofelectronic image stabilization functions, and the circumstance differsdepending on each type. Then, the electronic image stabilizationfunction will be briefly described below.

First, as camera shake measurement means, for example, means formeasuring a camera shake by a sensor, such as a gyro sensor, attached ona camera in order to detect a camera shake or means for measuring acamera shake by analyzing an image shot with a camera are conceivable.In the case of means for analyzing an image shot with a camera, it isdesirable that the motion blur measurement chart includes a patterncontaining a real picture as well as a geometric pattern. In this case,it is desirable to use a chromatic pattern having a high chroma ratherthan an achromatic pattern. This is because it becomes easy to recognizea feature point in a shot image.

Next, as camera shake correcting means, for example, means for reducingblurring of a shot image by image processing, or means for taking aplurality of images with a short exposure time and then combining theshot images while changing an area to be cut from the shot images areconceivable.

In either of the above electronic image stabilization methods, themeasurement method according to embodiment 1 is applicable.Specifically, procedures such as an evaluation value calculationprocedure taking a bokeh offset amount into consideration and, a motionblur amount measurement procedure of actually measuring a distance in aspecific level range and estimating a bokeh amount at the boundarybetween different color areas based on the measurement, are applicableto a camera of either of the above electronic image stabilization types.

1-3. Vibratory Apparatus

FIG. 4 is a block diagram showing the configuration of the vibratoryapparatus 100.

The vibratory controller 110 performs transmission and reception withthe computer 200 via an input section 111. The vibratory controller 110receives vibration data and the like from the computer 200, and feedsback the operation status of the vibratory apparatus 100 to the computer200. Upon control of the vibratory apparatus 100, the vibratorycontroller 110 uses a memory 112 as a working memory. The vibration datatransmitted from the computer 200 is stored into the memory 112. Byreferring to vibration data stored in the memory 112, the vibratorycontroller 110 controls a pitch direction motor driver 114 and a yawdirection motor driver 113.

The pitch direction motor driver 114 controls a pitch direction motor141. The pitch direction vibrating mechanism 140 includes a mechanicalcomponent such as a rotational shaft, besides the pitch direction motor141. In addition, the operation of the pitch direction motor 141 is fedback to the vibratory controller 110 via the pitch direction motordriver 114.

The yaw direction motor driver 113 controls a yaw direction motor 131.The yaw direction vibrating mechanism 130 includes a mechanicalcomponent such as a rotational shaft, besides the yaw direction motor131. In addition, the operation of the yaw direction motor 131 is fedback to the vibratory controller 110 via the yaw direction motor driver113

The vibratory controller 110 controls the release button pressingmechanism 150 in accordance with an instruction from the computer 200.

1-4. Vibration Data

FIGS. 5 and 6 are waveform diagrams showing examples of vibration datasent from the computer 200 to the vibratory apparatus 100. Thehorizontal axis indicates time and the vertical axis indicatesamplitude. FIG. 5 shows vibration data (for convenience, this vibrationdata is referred to as first vibration data) used for measuring a camerahaving a mass smaller than a first mass. FIG. 6 shows vibration data(for convenience, this vibration data is referred to as second vibrationdata) used for measuring a camera having a mass larger than a secondmass. The second mass is equal to or larger than the first mass. In eachof FIGS. 5 and 6, vibration data in the yaw direction and vibration datain the pitch direction are both indicated.

In the measurement method of embodiment 1, when the mass of the camera400 to be measured is smaller than the first mass, the first vibrationdata shown in FIG. 5 is selected, and meanwhile, when the mass of thecamera 400 to be measured is larger than the second mass, the secondvibration data shown in FIG. 6 is selected. In essence, in accordancewith the mass of the camera 400 to be measured, one of several kinds ofvibration data is selected. Then, the vibratory table 120 of thevibratory apparatus 100 is vibrated in accordance with the selectedvibration data. Next, while the vibratory table 120 is being vibrated,the motion blur measurement chart 300 is imaged by the camera 400 to bemeasured to acquire an evaluation image, and a motion blur amount in theimage is measured based on the acquired evaluation image.

As is obvious from FIGS. 5 and 6, the magnitude of the amplitude in alow frequency region normalized by the magnitude of the amplitude in ahigh frequency region in the first vibration data shown in FIG. 5 islarger than that in the second vibration data shown in FIG. 6. This isto take into consideration the fact that, in the case of taking an imagewith a light camera, a camera shake component with a low frequencybecomes large because the camera is light and a photographer usuallyholds a camera with the eyes away from a back-side monitor upon takingan image. On the other hand, in the case of a heavy camera, in the firstplace, camera shake of a low frequency hardly occurs because the camerais heavy. In addition to this, in the case of a heavy camera, the factthat a photographer usually takes an image with the eyes close to apeep-type viewfinder is also taken into consideration.

Next, a procedure for generating the vibration data shown in FIGS. 5 and6 will be described with reference to FIGS. 7 to 9. FIG. 7 is aflowchart showing a procedure for generating the vibration data. FIGS. 8and 9 are conceptual diagrams showing the content of each processingstep of the generation procedure.

First, measured data of a vibration waveform (camera shake waveform)applied to a camera due to camera shake at the time of imaging isacquired (S510). For example, a gyro sensor is attached on the camera,and then a photographer actually performs an imaging operation.Specifically, a photographer performs a pressing operation for a releasebutton, holding the camera with the hand. Then, from the output of thegyro sensor at the time of imaging, measured data of vibration waveformsin the yaw direction and the pitch direction is acquired. At this time,the output of the gyro sensor is an angular velocity of the vibrationwaveform applied to the camera. Therefore, by integrating the angularvelocity, a vibration waveform of the camera converted into angle can beacquired. Here, the time of imaging is a certain period including arelease timing.

The purpose of acquisition of measured data of a camera shake waveformis to obtain data as a base for generating the first vibration data orthe second vibration data. Therefore, it is desirable to acquire databased on as many photographers as possible and as many imaging scenes aspossible.

Next, the measured data of the camera shake waveform in each of the yawdirection and the pitch direction is converted into frequency-amplitudedata (S520). This conversion is performed by Fourier transform.

Next, the data in the yaw direction and the pitch direction afterFourier transform is divided into frequency component data (S530). Forexample, if frequencies are divided into bands at intervals of 1 Hz byFourier transform, the first amplitude data An indicates an amplitudecomponent in a frequency band of 1 Hz±0.5 Hz, and A2n indicates anamplitude component of 2 Hz±0.5 Hz. Since the frequency band of camerashake is about 20 Hz at the highest, the data may be extracted up tothat frequency. The processing of steps S520 and S530 is performed forall the pieces of measured data of the camera shake waveforms that havebeen acquired.

Next, based on all the pieces of yaw direction data processed by thesteps up to S530, the average value of amplitude data is calculated foreach frequency component data to obtain A₁₃ avenY, A_ave2nY, etc.(S540). Also for the pitch direction, A_avenP, A_ave2nP, etc. arecalculated in the same manner (S540).

Next, inverse Fourier transform is performed for A_avenY, A_ave2nY, etc.which are the average values of the amplitude data of respectivefrequency component data for the yaw direction, thereby calculatingvibration waveforms WnY, W2nY, etc. in respective specific bands for theyaw direction (S550). Also for the pitch direction, vibration waveformsWnP, W2nP, etc. are calculated in the same manner (S550).

Finally, the vibration waveforms WnY, W2nY, etc. in the respectivespecific bands for the yaw direction are summed to generate a camerashake model waveform WY_model for the yaw direction (S560). Upon summingthe vibration waveforms WnY, W2nY, etc. in the respective specificbands, they are summed with their phases being shifted randomly. Alsofor the pitch direction, a camera shake model waveform WP_model isgenerated in the same manner (S560). Upon summing the vibrationwaveforms in the respective specific bands for the pitch direction, thesame phase amounts as those used in the shifting for the yaw directionmay be used, or other phase amounts may be used. Vibration dataindicating these model waveforms is the first vibration data or thesecond vibration data.

Thus, since the first vibration data and the second vibration data areobtained by performing statistic processing for measured data about avibration, vibration data simulating a real vibration can be obtained.

1-5. Configuration of Computer

FIG. 10 is a block diagram showing the configuration of the computer200.

A CPU 210 controls a monitor 230, a hard disk 240, a memory 250, a firstcommunication section 260, and a second communication section 270 inaccordance with an instruction from a keyboard 220. The firstcommunication section 260 is connected to the camera 400 to be measuredand performs transmission and reception of data with the camera 400 tobe measured. The second communication section 270 is connected to thevibratory apparatus 100 and performs transmission and reception of datawith the vibratory apparatus 100. The first communication section 260and the second communication section 270 may be a wired connection unitsuch as a USB or a wireless connection unit, for example.

The CPU 210 may be configured to acquire information about the settingsof the camera 400 to be measured such as the focal length and theshutter speed value, from the camera 400 to be measured via the firstcommunication section 260. In addition, the CPU 210 may be configured toacquire image data from the camera 400 to be measured via the firstcommunication section 260. In addition, the CPU 210 may be configured totransmit a signal indicating a shutter release instruction to the camera400 to be measured via the first communication section 260.

The hard disk 240 stores two kinds of vibration data shown in FIGS. 5and 6. The hard disk 240 stores software such as a motion blurmeasurement software 500 and an evaluation value calculation software600 described later. Such software is realized as a computer program. Acomputer program indicating such software may be stored in an opticaldisc and be installed into the computer 200 from the optical disc, or acomputer program indicating such software may be stored into the harddisk 240 via a network and then installed into the computer 200. Thesoftware stored into the hard disk 240 is loaded onto the memory 250 asnecessary, to be executed by the CPU 210. The computer program forrealizing such software can be stored into a storage medium such as amemory card, a magnetic disk, or a magnetic tape, besides an opticaldisc or a hard disk.

The CPU 210 transmits vibration data stored in the hard disk 240 to thevibratory apparatus 100 via the second communication section 270. Inaddition, the CPU 210 receives a signal indicating the operation stateof the vibratory apparatus 100 from the vibratory apparatus 100 via thesecond communication section 270.

The CPU 210 uses the memory 250 as a working memory. The monitor 230displays a calculation result and the like obtained by the CPU 210.

1-6. Configurations of Motion Blur Measurement Software and EvaluationValue Calculation Software

FIG. 11 is a block diagram showing the configuration of the motion blurmeasurement software 500. The motion blur measurement software 500 issoftware for measuring a bokeh offset amount and a measuredcomprehensive bokeh amount from an image obtained by imaging the motionblur measurement chart 300. Here, the bokeh offset amount is a bokehamount of a shot image due to a factor other than camera shake, andspecifically, is a numerical value that is unique to each device andthat depends on the optical performance, effective pixels, imageprocessing, and the like of the camera 400 to be measured. In addition,the measured comprehensive bokeh amount is a measured value of a bokehamount of an image taken with the image stabilization function being ON,when the camera 400 to be measured is vibrated based on a vibrationwaveform (waveform indicated by the vibration data). A task managementsection 510 performs overall task management. The processing contents ofblocks from an image signal acquiring section 520 to a multiplicationprocessing section 590 will be described later, together with thedescription of a camera shake measurement procedure (FIG. 16) which willbe also described later.

FIG. 12 is a block diagram showing the configuration of the evaluationvalue calculation software 600. The evaluation value calculationsoftware 600 is software for calculating an evaluation value indicatingthe performance of an image stabilization function of the camera 400 tobe measured. A task management section 610 performs overall taskmanagement. A bokeh offset amount measurement section 622 and a measuredcomprehensive bokeh amount measurement section 642 are blocksincorporating the motion blur measurement software 500 or using themotion blur measurement software 500. That is, the motion blurmeasurement software 500 can be also regarded as subroutine software ofthe evaluation value calculation software 600. The processing contentsof blocks from a static state image acquiring section 621 to an imagestabilization performance evaluation value calculation section 650 willbe described later, together with the description of an evaluation valuecalculation procedure (FIG. 18) which will be also described later.

2. Evaluation Procedure

An evaluation procedure for measuring the performance of the imagestabilization function of the camera 400 to be measured by using themeasurement system configured as described above, will be described withreference to FIG. 13.

The camera 400 to be measured is placed on the vibratory table 120, andthen the camera 400 to be measured takes an image of the motion blurmeasurement chart 300 without shaking the vibratory table 120, therebygenerating a static state image (S100). Next, the camera 400 to bemeasured is fixed on the vibratory table 120, and then the camera 400 tobe measured takes an image of the motion blur measurement chart 300 withthe vibratory table 120 being vibrated, thereby generating a vibratedstate image (S200). Here, both the static state image and the vibratedstate image are still images. Finally, based on the static state imageand the vibrated state image that have been taken and the setting valuesof the camera 400 to be measured, the computer 200 measures orcalculates a theoretical motion blur amount, a bokeh offset amount, anestimated comprehensive bokeh amount, a measured comprehensive bokehamount, a reference motion blur amount, a measured motion blur amount, areference shutter speed value, and a measured shutter speed value. Then,the computer 200 calculates an evaluation value indicating theperformance of the image stabilization function of the camera 400 to bemeasured.

Here, the theoretical motion blur amount is a theoretical value of amotion blur amount that can be measured from an image that would beobtained with the image stabilization function being OFF (in the case ofa camera not having OFF setting, assumed to be OFF) when the camera 400to be measured is vibrated based on a vibration waveform.

In addition, the estimated comprehensive bokeh amount is a theoreticalestimated value of a bokeh amount of an image that would be obtainedwith the image stabilization function being OFF (in the case of a cameranot having OFF setting, assumed to be OFF) when the camera 400 to bemeasured is vibrated based on a vibration waveform. The estimatedcomprehensive bokeh amount is represented as the square root of the sumof square of the bokeh offset amount and square of the theoreticalmotion blur amount.

In addition, the reference motion blur amount is a numerical value thatis a reference for calculating the image stabilization performance. Thereference motion blur amount is a numerical value obtained bysubtracting the bokeh offset amount from the estimated comprehensivebokeh amount.

In addition, the measured motion blur amount is a numerical valueindicating the remaining camera shake that has not been correctedeventually when the image stabilization function of the camera 400 to bemeasured is ON. The measured motion blur amount is obtained bysubtracting the bokeh offset amount from the measured comprehensivebokeh amount.

2-1. Static State Imaging Procedure

The details of a static state imaging procedure (S100) will be describedwith reference to a flowchart shown in FIG. 14.

First, the camera 400 to be measured is placed on the vibratory table120 (S101). In the static state imaging, since the vibratory table 120is not vibrated upon imaging, the camera 400 to be measured may notnecessarily be fixed on the vibratory table 120. However, it ispreferable that the camera 400 to be measured is fixed on the vibratorytable 120 in order to ensure the stability of measurement and workingcontinuity to vibrated state imaging described later. It is preferablethat the distance (imaging distance) from the camera 400 to be measuredto the motion blur measurement chart 300 is set such that the areadefined by the imaging area marker 303 shown in FIG. 2 is the imagingarea.

Next, the imaging conditions of the camera 400 to be measured such as afocal length and an image stabilization mode are set (S102). In thestatic state imaging, it is desirable that the image stabilizationfunction is OFF. However, in some cameras, the image stabilizationfunction cannot be turned off. In such a case, since the camera isstatic upon imaging, the imaging may be performed with the imagestabilization function being ON under the assumption that the imagestabilization function is not exerted.

Next, the shutter speed value of the camera 400 to be measured is set(S103). For example, an initial shutter speed value is set to about1/focal length (35 mm film equivalent). In both of static state imaging(S200) and vibrated state imaging (S300), a plurality of images need tobe taken for each of a plurality of shutter speeds. Accordingly, after aplurality of images are taken with the same shutter speed value, theshutter speed value is sequentially set again so as to be slowed down byup to one stop, and thus the same imaging is repeated until the shutterspeed value reaches a necessary and sufficient value.

Next, the release button pressing mechanism 150 is driven to cause thecamera 400 to be measured to take an image (S104). The controller 440stores the shot image into the memory card 451, in a form of image filehaving a header added thereto, the header storing imaging conditioninformation such as information indicating the focal length, the shutterspeed value, and the image stabilization mode. Thus, the shot image canbe stored so as to be associated with the imaging condition.

Next, the CPU 210 determines whether or not a predetermined number ofimages have been taken for all of the intended shutter speed values(S105), and then if such imaging has been completed (Yes in S105), endsthe static state imaging procedure.

On the other hand, if such imaging has not been completed yet (No inS105), the CPU 210 determines whether or not to change the shutter speedvalue (S106). This determination is performed based on whether or notthe predetermined number of images have been taken for the shutter speedvalue that is currently set. If the shutter speed value is not changed(No in S106), the process returns to step S104 to perform again thestatic state imaging with the shutter speed value that is currently set.If the shutter speed value is changed (Yes in S106), the process returnsto step S103 to change the shutter speed value and then the static stateimaging is performed again.

As a result of the above static state imaging procedure, the memory card451 stores the predetermined number of static state images for each ofthe plurality of shutter speed values. Here, it is preferable that thepredetermined number is about 10 or more for each shutter speed.

2-2. Vibrated State Imaging Procedure

Next, the details of the vibrated state imaging procedure (S200) will bedescribed with reference to a flowchart shown in FIG. 15.

First, the camera 400 to be measured is fixed on the vibratory table 120(S201). If the camera 400 to be measured has been fixed on the vibratorytable 120 in step S101 in the static state imaging, the static stateimaging can be directly shifted to the vibrated state imaging in thesame state. As in the static state imaging, it is preferable that thedistance (imaging distance) from the camera 400 to be measured to themotion blur measurement chart 300 is set such that the area defined bythe imaging area marker 303 shown in FIG. 2 is the imaging area.

Next, the operation condition of the vibratory table 120 is set (S202).An evaluator selects the first vibration data shown in FIG. 5 or thesecond vibration data shown in FIG. 6 in accordance with the mass of thecamera 400 to be measured. Specifically, for example, if the mass of thecamera 400 to be measured is smaller than the first mass, the firstvibration data is selected from among a plurality of pieces of vibrationdata, and if the mass of the camera 400 to be measured is larger thanthe second mass, the second vibration data is selected from among theplurality of pieces of vibration data. The vibration data selected bythe evaluator is given to the vibratory controller 110 from the computer200.

Next, the imaging conditions of the camera 400 to be measured are set(S203). In the vibrated state imaging, the image stabilization functionis set to ON. The focal length of the camera 400 to be measured is setat the same value as in the static state imaging.

Next, based on the vibration data selected by the evaluator, thevibratory table 120 is vibrated (S204).

Next, the shutter speed value of the camera 400 to be measured is set(S205). For example, the way of setting an initial shutter speed valueand changing the shutter speed value thereafter is the same as in thestatic state imaging.

Next, the release button pressing mechanism 150 is driven to cause thecamera 400 to be measured to take an image (S206). The way of storingthe shot image into the memory card 451, and the like are the same as inthe static state imaging.

Next, the CPU 210 determines whether or not a predetermined number ofimages have been taken for all of the intended shutter speed values(S207), and then if such imaging has been completed (Yes in S207), endsthe vibrated state imaging procedure.

On the other hand, if such imaging has not been completed yet (No inS207), the CPU 210 determines whether or not to change the shutter speedvalue (S208). This determination is performed based on whether or notthe predetermined number of images have been taken for the shutter speedvalue that is currently set. If the shutter speed value is not changed(No in S208), the process returns to step S206 to perform again thevibrated state imaging with the shutter speed value that is currentlyset. If the shutter speed value is changed (Yes in S208), the processreturns to step S205 to change the shutter speed value and then thevibrated state imaging is performed again.

As a result of the above vibrated state imaging procedure, the memorycard 451 stores the predetermined number of vibrated state images foreach of the plurality of shutter speed values. Here, it is preferablethat the predetermined number is about 200 or more for each shutterspeed. The reason for taking many images is that there are variations inthe motion blur amounts of the images and therefore it is necessary toperform statistic processing such as average value calculation about themotion blur amounts of the images.

2-3-1. Camera Shake Measurement Procedure

Before the description of a calculation procedure for an evaluationvalue indicating the performance of the image stabilization function ofthe camera 400 to be measured, a camera shake measurement procedure willbe described with reference to FIG. 16. It is noted that the camerashake measurement procedure is executed as a part of the evaluationvalue calculation procedure. In addition, the camera shake measurementprocedure is executed by the motion blur measurement software shown inFIG. 11, using hardware resources of the computer 200. Therefore, FIG.11 will be referred to as necessary in the description.

First, an image signal acquiring section 520 causes the computer 200 toacquire an image signal for evaluation (S401). More specifically, theCPU 210 acquires an image signal stored in the memory card 451 byconnecting the memory card 451 to the computer 200 or from the camera400 to be measured via the first communication section 260, and thenstores the image signal into the hard disk 240 or the memory 250. Theimage signal to be acquired may be an image signal indicating a staticstate image or an image signal indicating a vibrated state image.

Next, a level value acquiring section 530 causes the computer 200 toacquire, from the shot image signal, the level value of an image signalof the black area 301 and the level value of an image signal of thewhite area 302 shown in FIG. 2 (S402). Here, the level of an imagesignal refers to a predetermined physical quantity about the imagesignal, e.g., the brightness of the image signal.

Next, a normalizing section 540 causes the computer 200 to normalize thelevel value of the shot image signal with reference to a specific range(S403). For example, in the case where “10” is acquired as the levelvalue of the image signal of the black area 301, “245” is acquired asthe level value of the image signal of the white area 302, and thenormalization is performed in a range of “0 to 255”, the level value ofthe image signal of the black area 301 is set at “0” (hereinafter, forconvenience, referred to as a first level value), and the level value ofthe image signal of the white area 302 is set at “255” (hereinafter, forconvenience, referred to as a second level value).

FIG. 17 is a graph showing variation in the normalized level values atthe boundary between the black area 301 and the white area 302. In FIG.17, the horizontal axis indicates the number of a pixel formed on theCCD image sensor 420. The normalizing section 540 causes the computer200 to normalize all the level values based on measured values at apixel P1 in the black area 301 and a pixel P6 in the white area 302, forexample.

Next, a difference calculation section 550 causes the computer 200 tocalculate the difference between the level value of the image signal ofthe black area 301 and the level value of the image signal of the whitearea 302 (S404). In this case, these level values have been normalizedin a range of “0 to 255” and therefore naturally, the difference becomes255. This step S404 has a significance mainly when camera shakemeasurement is performed without normalization of the level values.

Next, a corrected level value calculation section 560 causes thecomputer 200 to calculate a first corrected level value by adding X% ofthe calculated difference to the first level value, and to calculate asecond corrected level value by subtracting Y% of the calculateddifference from the second level value. Specifically, if X% is 10% andY% is 10%, the first corrected level value is “25.5” and the secondcorrected level value “229.5”.

Next, a corrected level position specifying section 570 causes thecomputer 200 to specify a pixel position where the level value is thefirst corrected level value, as a first corrected level position, and apixel position where the level value is the second corrected levelvalue, as a second corrected level position, at the boundary between theblack area 301 and the white area 302. With reference to FIG. 17, apixel P3 is the first corrected level position and a pixel P4 is thesecond corrected level position.

Next, a distance calculation section 580 causes the computer 200 tocalculate the distance between the first corrected level position andthe second corrected level position (S407). With reference to FIG. 17, adistance A is the calculated distance. The distance A is a distanceconverted in 35 mm film equivalent from the number of pixels between thepixel P3 and the pixel P4.

Finally, a multiplication processing section 590 multiplies the distancecalculated in step S407 by 100/(100−X−Y) (S408). With reference to FIG.17, since X% and Y% are both 10%, the distance A is multiplied by 10/8.The value thus calculated corresponds to an estimated value of adistance B. The distance B is a distance converted in 35 mm filmequivalent from the number of pixels between the pixel P2 and the pixelP5.

The reason for actually measuring the distance in a specific level rangeand then estimating a bokeh amount at the boundary between the blackarea 301 and the white area 302 based on the measured distance, is toexclude the influence of noise at the boundary (the vicinity of thepixel P2 in FIG. 17) between the black area 301 and the bokeh area orthe boundary (the vicinity of the pixel P5 in FIG. 17) between the whitearea 302 and the bokeh area. This is because the influence of noise isparticularly likely to appear in the vicinity of such boundaries.

2-3-2. Evaluation Value Calculation Procedure

With reference to FIG. 18, the calculation procedure for an evaluationvalue indicating the performance of the image stabilization function ofthe camera 400 to be measured, will be described. In the followingdescription, FIGS. 19 to 22 will be referred to as necessary. Thesefigures are characteristic graphs of a camera shake, in which thehorizontal axis indicates a shutter speed value and the vertical axisindicates a camera shake. In addition, evaluation value calculationprocedure is realized by the evaluation value calculation software shownin FIG. 12, using the hardware resources of the computer 200. Therefore,the description will be performed by referring to FIG. 12 as necessary.

First, a theoretical motion blur amount calculation section 631 causesthe computer 200 to acquire the focal length set on the camera 400 to bemeasured, calculate a focal length in 35 mm film equivalent from theacquired focal length, and then calculate a theoretical motion bluramount by using the focal length in 35 mm film equivalent (S301).Regarding the acquisition of the focal length, a value inputted via thekeyboard 220 by an evaluator may be accepted, a setting value may bereceived from the camera 400 to be measured, or the value may be readfrom the header of an image file. The theoretical motion blur amount iscalculated based on the following expression.

Theoretical motion blur amount [μm]=Focal Length in 35 mm FilmEquivalent [mm]×tan θ×1000

Here, θ is referred to as an average vibration angle which is theaverage value for each shutter speed, of camera shake angles that wouldoccur when the camera is vibrated based on the vibration data. Since twokinds of vibration data are prepared as shown in FIGS. 5 and 6, at leasttwo kinds of average vibration angles θ are prepared, too. Since theaverage vibration angle θ increases as the shutter speed valueincreases, the theoretical motion blur amount draws a trajectoryschematically shown in FIG. 19.

Next, a static state image acquiring section 621 causes the computer 200to acquire a plurality of static state images obtained by imaging themotion blur measurement chart 300 a plurality of times for each of theplurality of shutter speeds (S302). More specifically, the CPU 210acquires the static state images stored in the memory card 451 byconnecting the memory card 451 to the computer 200 or from the camera400 to be measured via the first communication section 260, and thenstores the static state images into the hard disk 240 or the memory 250.

Next, a bokeh offset amount measurement section 622 causes the computer200 to measure, as a bokeh offset amount, a bokeh amount at the boundarybetween different color areas (in embodiment 1, between the black area301 and the white area 302) in the acquired static state images, foreach of the plurality of shutter speeds (S303). The measurement of thebokeh offset amount is performed using the motion blur measurementsoftware 500 shown in FIG. 11, as described above.

Next, an estimated comprehensive bokeh amount calculation section 632causes the computer 200 to calculate an estimated comprehensive bokehamount for each of the plurality of shutter speeds by superimposing themeasured bokeh offset amount onto the calculated theoretical motion bluramount for each of the plurality of shutter speeds (S304). The estimatedcomprehensive bokeh amount is represented as the square root of the sumof square of the theoretical motion blur amount and square of the bokehoffset amount, for example. As a result, the estimated comprehensivebokeh amount draws a trajectory schematically shown in FIG. 20. Bysuperimposing the bokeh offset amount onto the theoretical motion bluramount, as shown in FIG. 20, as well as increase in the value of theestimated comprehensive bokeh amount, the change rate of the slope ofthe tangent of the curve changes. This is due to the influence of thebokeh offset amount, that is, this means that the influence of a bokehof an image intrinsic to the camera 400 to be measured is incorporatedinto the present evaluation value calculation procedure. More simply, inthe case of a camera intrinsically having a small bokeh amount, thecurve of the estimated comprehensive bokeh amount is close to the curveof the theoretical motion blur amount, and on the other hand, in thecase of a camera intrinsically having a large bokeh amount, the curve ofthe estimated comprehensive bokeh amount is far from the curve of thetheoretical motion blur amount, and also, the change rate of the slopeof the tangent thereof is small.

Next, a vibrated state image acquiring section 641 causes the computer200 to acquire a plurality of vibrated state images obtained by imagingthe motion blur measurement chart 300 a plurality of times for each ofthe plurality of shutter speeds (S305). More specifically, the CPU 210acquires the vibrated state images stored in the memory card 451 byconnecting the memory card 451 to the computer 200 or from the camera400 to be measured via the first communication section 260, and storesthe vibrated state images into the hard disk 240 or the memory 250.

Next, a measured comprehensive bokeh amount measurement section 642causes the computer 200 to measure, as a measured comprehensive bokehamount, a bokeh amount at the boundary between different color areas inthe acquired vibrated state images, for each of the plurality of shutterspeeds (S306). The measurement of the measured comprehensive bokehamount is performed using the motion blur measurement software 500 shownin FIG. 11, as described above. The measured comprehensive bokeh amountis measured as a bokeh amount in 35 mm film equivalent. As a result, themeasured comprehensive bokeh amount draws a trajectory schematicallyshown in FIG. 21.

Next, a reference motion blur amount calculation section 633 causes thecomputer 200 to calculate a reference motion blur amount for each of theplurality of shutter speed values by subtracting the measured bokehoffset amount from the calculated estimated comprehensive bokeh amount(S307).

Next, a measured motion blur amount calculation section 643 causes thecomputer 200 to calculate a measured motion blur amount for each of theplurality of shutter speed values by subtracting the measured bokehoffset amount from the measured comprehensive bokeh amount (S308). Atthis time, if the measured motion blur amount becomes a negative value,the measured motion blur amount is made to be zero. As a result, thereference motion blur amount and the measured motion blur amount drawtrajectories schematically shown in FIG. 22.

Next, a reference shutter speed value calculation section 634 causes thecomputer 200 to calculate a shutter speed value that causes a specificmotion blur amount, as a reference shutter speed value, by using theplurality of reference motion blur amounts that have been calculated(S309). The specific motion blur amount is, for convenience, referred toas a determination level for image stabilization function. In FIG. 22, ashutter speed value indicated by “SS_OFF” is the reference shutter speedvalue.

Next, a measured shutter speed value calculation section 644 causes thecomputer 200 to calculate a shutter speed value that causes the specificmotion blur amount, as a measured shutter speed value, by using theplurality of measured motion blur amounts that have been calculated(S310). In FIG. 22, a shutter speed value indicated by “SS_ON” is themeasured shutter speed value.

Finally, an image stabilization performance evaluation value calculationsection 650 causes the computer 200 to calculate an evaluation valueindicating the performance of the image stabilization function of thecamera 400 to be measured for the focal length at which the imaging hasbeen performed, by using the reference shutter speed value and themeasured shutter speed value (S311). In FIG. 22, a stop number ofshutter speed between “SS_OFF” and “SS_ON” corresponds to the aboveevaluation value.

Thus, the evaluation value indicating the performance of the imagestabilization function can be calculated. In the procedure shown inembodiment 1, the influence of the bokeh offset amount is reflected incalculation of the estimated comprehensive bokeh amount and thereference motion blur amount. This is an important matter for enhancingthe accuracy of the evaluation value. Then, hereinafter, the influenceof the bokeh offset amount will be described in detail with reference toFIGS. 23 to 26.

In the following description, for facilitating the description, a cameraA to be measured and a camera B to be measured having the same mass, thesame focal length, and the same performance of the image stabilizationfunction will be assumed. The bokeh offset amount of the camera A to bemeasured is smaller than that of the camera B to be measured. That is,the bokeh amount of an image intrinsic to the camera A to be measured issmall, and the bokeh amount of an image intrinsic to the camera B to bemeasured is large. FIGS. 23 and 24 are characteristic diagrams of amotion blur amount showing the trajectories of the theoretical motionblur amount, the reference motion blur amount, and the measured motionblur amount. FIG. 23 is a characteristic diagram for the camera A to bemeasured, and FIG. 24 is a characteristic diagram for the camera B to bemeasured.

As shown in FIG. 23, since the bokeh offset amount of the camera A to bemeasured is small, the trajectory of the reference motion blur amountalmost coincides with the trajectory of the theoretical motion bluramount. Therefore, even if the bokeh offset amount is not taken intoconsideration, that is, the theoretical motion blur amount is used asthe trajectory of a motion blur amount obtained when the imagestabilization function is OFF, the image stabilization performancecorresponds to the stop number between the shutter speed value SS1 andthe shutter speed value SS3. The image stabilization performance in thecase of taking the bokeh offset amount into consideration corresponds tothe stop number between the shutter speed value SS2 and the shutterspeed value SS3. Therefore, the difference between both cases is slightas shown by the stop number between the shutter speed value SS1 and theshutter speed value SS2. That is, in the case of the camera A to bemeasured having a small bokeh offset amount, even if an evaluation valueindicating the image stabilization performance is calculated withoutconsideration of the bokeh offset amount, a significant problem does notoccur so much.

On the other hand, in the case of the camera B to be measured having alarge bokeh offset amount, if an evaluation value indicating the imagestabilization performance is calculated without consideration of thebokeh offset amount, the calculated evaluation value deviates from theactual value, thus causing a significant problem. Hereinafter, thispoint will be described in detail.

First, since the camera A to be measured and the camera B to be measuredhave the same mass, the average vibration angles given in advance arethe same. In addition, since their focal lengths are also the same, thetheoretical motion blur amount of the camera A to be measured and thetheoretical motion blur amount the camera B to be measured are the same.Therefore, as shown in FIG. 24, a shutter speed value at theintersection of the trajectory of the theoretical motion blur amount andthe determination level for image stabilization performance becomes theshutter speed value SS1, in both cameras.

Next, since the bokeh offset amount of the camera B to be measured islarge, as shown in FIG. 25, the trajectory of the measured comprehensivebokeh amount of the camera B to be measured is more gradual than thetrajectory of the measured comprehensive bokeh amount of the camera A tobe measured. The reason is as follows. That is, in the case of a camerahaving a large bokeh offset amount, in a region where the shutter speedvalue is small, the bokeh offset amount is more dominant to the measuredcomprehensive bokeh amount than a bokeh due to a camera shake, andmeanwhile, in a region where the shutter speed value is large, theinfluence of a bokeh due to a camera shake becomes large, so that thedifference in the measured comprehensive bokeh amount between the cameraA to be measured and the camera B to be measured becomes small.Accordingly, by subtracting the bokeh offset amount from the measuredcomprehensive bokeh amount shown in FIG. 25, the measured motion bluramounts shown in FIG. 26 are obtained.

Here, if an evaluation value indicating the image stabilizationperformance is calculated from the stop number between the shutter speedvalue SS1 and the shutter speed value SS5 with reference to thetheoretical motion blur amount without consideration of the bokeh offsetamount, the camera B to be measured intrinsically having a large bokehamount of an image is evaluated to have a higher performance of theimage stabilization function even though the camera A to be measured andthe camera B to be measured actually have the same performance of theimage stabilization function. This is obviously inappropriate as anevaluation method.

Accordingly, in the present application, the bokeh offset amount istaken into consideration upon calculation of an evaluation valueindicating the performance of the image stabilization function.Specifically, upon calculation of the reference motion blur amount, thebokeh offset amount is superimposed onto the theoretical motion bluramount, thereby calculating the estimated comprehensive bokeh amount.Then, the bokeh offset amount is subtracted from the estimatedcomprehensive bokeh amount, thereby obtaining the reference motion bluramount. Thus, in the case of a camera having a large bokeh offsetamount, the trajectory of the reference motion blur amount becomes awayfrom the trajectory of the theoretical motion blur amount. That is, theshutter speed value (SS4) at the intersection of the trajectory of thereference motion blur amount and the determination level for imagestabilization performance shown in FIG. 24 is larger than such a shutterspeed value (SS2) in the case of the camera A to be measured shown inFIG. 23. Therefore, the stop number between the shutter speed value SS1and the shutter speed value SS4 becomes larger than the stop numberbetween the shutter speed value SS1 and the shutter speed value SS2. Asa result, in the camera B to be measured, the evaluation valueindicating the image stabilization performance becomes small which isobtained based on the stop number between the shutter speed value (SS4)at the intersection of the reference motion blur amount and thedetermination level for image stabilization function, and the shutterspeed value (SS5) at the intersection of the measured motion blur amountand the determination level for image stabilization performance. Thus,the evaluation value becomes close to the evaluation value (the stopnumber between the shutter speed value SS2 and the shutter speed valueSS3 shown in FIG. 23) obtained for the camera A to be measured, wherebya more appropriate evaluation value can be obtained.

To summarize, as is obvious from FIGS. 23 to 26, the larger the bokehamount intrinsic to a camera to be measured is, the more gradual thetrajectory of the measured motion blur amount is. Therefore, if anevaluation value indicating the performance of the image stabilizationfunction is calculated based on the reference motion blur amountcalculated without consideration of the bokeh offset amount, the resultis that the larger the bokeh offset amount of a camera to be measuredis, the higher the performance of the image stabilization function is.In order to avoid such a result, as in embodiment 1, the bokeh offsetamount has been taken into consideration upon calculation of anevaluation value indicating the performance of the image stabilizationfunction.

Embodiment 2

In embodiment 1, the motion blur measurement software has been used forevaluation of the performance of the image stabilization function.Instead, for example, the motion blur measurement software may beincorporated into a camera.

By thus incorporating the motion blur measurement software, a bokehamount of a shot image can be measured more accurately. This softwarecan be utilized for a function of alerting a user that a shot image isblurred after the imaging or a function of correcting the bokeh of theshot image through image processing.

Embodiment 3

In embodiment 1, an evaluator has selected vibration data in accordancewith the mass of the camera 400 to be measured. However, the computer200 may select vibration data. In this case, the computer 200 functionsas: a selection section for selecting one of a plurality of pieces ofvibration data in accordance with the mass of the camera 400 to bemeasured; a vibration control section for shaking the vibratory table120 of the vibratory apparatus 100 on which the camera 400 to bemeasured is fixed, in accordance with the selected vibration data; anacquiring section for acquiring an evaluation image taken and generatedby the camera 400 to be measured while the vibratory table 120 is beingvibrated; and a measurement section for measuring a motion blur amountof an image based on the acquired evaluation image. Thus, an evaluator'soperation to select vibration data can be omitted.

Alternatively, a computer program including: a selection section forcausing the computer 200 to select one of a plurality of pieces ofvibration data in accordance with the mass of the camera 400 to bemeasured; a vibration control section for controlling the computer 200so as to vibrate the vibratory table 120 of the vibratory apparatus 100on which the camera 400 to be measured is fixed, in accordance with theselected vibration data; an acquiring section for causing the computer200 to acquire an evaluation image taken and generated by the camera 400to be measured while the vibratory table 120 is being vibrated; and ameasurement section for causing the computer 200 to measure a motionblur amount of an image based on the acquired evaluation image, may beinstalled into the computer 200, whereby the measurement of motion bluramount of a camera may be realized. Such a computer program can bestored in a storage medium such as a memory card, an optical disc, ahard disk, or a magnetic tape. Thus, by realizing the measurement methodfor a motion blur amount of a camera as a computer program, it becomespossible to measure a motion blur amount of a camera, using atotal-purpose computer.

In embodiment 3, the computer 200 acquires the mass of the camera 400 tobe measured by any means. For example, an evaluator may input mass dataof the camera 400 to be measured via the keyboard 220. Thus, anevaluator's operation to select vibration data can be omitted.Alternatively, a weight scale may be provided for the vibratoryapparatus 100, and then mass data of the camera 400 to be measured maybe acquired from the vibratory apparatus 100. Thus, the trouble for theevaluator to select vibration data or input the mass data can be saved.

Other Embodiments

As embodiments of the present disclosure, the above embodiments 1 to 3have been described. However, the present disclosure is not limited toembodiments 1 to 3, but may be used with modifications as appropriate.Then, other embodiments of the present disclosure will be collectivelydescribed in this section below.

In embodiment 1, the estimated comprehensive bokeh amount is calculatedbased on the theoretical motion blur amount and the bokeh offset amount,the bokeh offset amount is subtracted from each of the estimatedcomprehensive bokeh amount and the measured comprehensive bokeh amount,and then shutter speed values at the determination level for imagestabilization performance are read, whereby an evaluation value of animage stabilization performance is calculated. However, the presentdisclosure is not limited thereto. For example, after the estimatedcomprehensive bokeh amount is calculated based on the theoretical motionblur amount and the bokeh offset amount, shutter speed values at a levelobtained by adding the bokeh offset amount to the determination levelfor image stabilization performance may be read from the estimatedcomprehensive bokeh amount and the measured comprehensive bokeh amount,whereby an evaluation value of an image stabilization performance may becalculated. In essence, an evaluation value indicating the performanceof an image stabilization function of a camera may be calculated basedon the theoretical motion blur amount, the bokeh offset amount, and themeasured comprehensive bokeh amount.

In embodiment 1, the functions of the motion blur measurement software500 and the evaluation value calculation software 600 have been realizedby using hardware resources of the computer 200, but the presentdisclosure is not limited thereto. For example, the computer 200 mayincorporate therein hardware such as wired logic for realizing thefunctions of the motion blur measurement software 500 and the evaluationvalue calculation software 600, thereby realizing the measurement of themotion blur amount and the calculation of the evaluation value.Alternatively, the functions of the motion blur measurement software 500and the evaluation value calculation software 600 may be realized byusing hardware resources of the vibratory apparatus 100. In essence, ameasurement device capable of realizing the functions of the motion blurmeasurement software 500 and the evaluation value calculation software600 may be provided in the measurement system shown in FIG. 1.

In embodiment 1, the evaluation system has been controlled by thecomputer 200, but the present disclosure is not limited thereto. Forexample, a camera to be measured may have such a control function.Specifically, the functions of the motion blur measurement software 500and the evaluation value calculation software 600 may be provided with acamera to be measured, so that the camera to be measured by itself cancalculate an evaluation value indicating the performance of an imagestabilization function based on a shot image. In addition, a camera tobe measured may have vibration data and the like stored therein, so thatthe camera to be measured can control the vibratory apparatus 100.

In embodiment 1, in the camera shake measurement procedure (FIG. 16),the level value has been normalized (S403) to conduct the measurementflow of the motion blur amount, but the present disclosure is notlimited thereto. For example, the measurement flow of the motion bluramount may be conducted without normalizing the level value.

In embodiment 1, the shutter speed value of the camera 400 to bemeasured has been set based on an instruction from the computer 200, butthe present disclosure is not limited thereto. For example, the shutterspeed value may be manually set by an evaluator before imaging of anevaluation image. Alternatively, in the case where the shutter speedvalue cannot be manually set, the shutter speed value automatically setby the camera 400 to be measured may be substantially set by adjustmentof the amount of light radiated to the motion blur measurement chart300.

The measurement method of the present disclosure can be used forevaluating the performance of an image stabilization function of acamera. The camera may be of any type as long as the camera has an imagestabilization function, including a consumer digital camera, aprofessional camera, a mobile phone with a camera function, or a cameraof a smartphone, and the like.

In addition, the camera shake measurement method of the presentdisclosure can be used not only for evaluation of a blur of an image butalso for camera shake evaluation about other images. For example, thecamera shake measurement method of the present disclosure can be usedfor camera shake evaluation about a shot image by providing the camerawith such a system. The camera may be of any type as long as the camerahas a hand shake correcting function, including a consumer digitalcamera, a professional camera, a mobile phone with a camera function, ora camera of a smartphone, and the like.

As presented above, embodiments have been described as examples of thetechnology according to the present disclosure. For this purpose, theaccompanying drawings and the detailed description are provided.

Therefore, components in the accompanying drawings and the detaildescription may include not only components essential for solvingproblems, but also components that are provided to illustrate the abovedescribed technology and are not essential for solving problems.Therefore, such inessential components should not be readily construedas being essential based on the fact that such inessential componentsare shown in the accompanying drawings or mentioned in the detaileddescription.

Further, the above described embodiments have been described toexemplify the technology according to the present disclosure, andtherefore, various modifications, replacements, additions, and omissionsmay be made within the scope of the claims and the scope of theequivalents thereof.

What is claimed is:
 1. A measurement method for a bokeh amount of animage, the measurement method comprising: acquiring an image signal byimaging an object with a camera, the object including a first color areacomposed of a first color, and a second color area which is composed ofa second color different from the first color and is adjacent to thefirst color area; acquiring a first level value that is a level value ofthe image signal in the first color area; acquiring a second level valuethat is a level value of the image signal in the second color area;calculating a difference between the first level value and the secondlevel value; calculating a first corrected level value by adding X% ofthe calculated difference to the first level value; calculating a secondcorrected level value by subtracting Y% of the calculated differencefrom the second level value; specifying a first corrected level positionand a second corrected level position at a boundary between the firstcolor area and the second color area included in the acquired imagesignal, the first corrected level position being a position where thelevel value of the image signal is the first corrected level value, andthe second corrected level position being a position where the levelvalue of the image signal is the second corrected level value;calculating a distance between the specified first corrected levelposition and the specified second corrected level position; andmeasuring a bokeh amount of the image at the boundary between the firstcolor area and the second color area by multiplying the calculateddistance by 100/(100−X−Y).
 2. The measurement method for a bokeh amountof an image, according to claim 1, wherein a level value indicated bythe acquired image signal is normalized with reference to a specificrange, and the normalized level value is used as the level value of theimage signal.
 3. A measurement apparatus comprising: an image acquiringsection configured to acquire an image signal generated by imaging of anobject with a camera, the object including a first color area composedof a first color, and a second color area which is composed of a secondcolor different from the first color and is adjacent to the first colorarea; a first level value acquiring section configured to acquire afirst level value that is a level value of the image signal in the firstcolor area; a second level value acquiring section configured to acquirea second level value that is a level value of the image signal in thesecond color area; a difference calculation section configured tocalculate a difference between the first level value and the secondlevel value; a first corrected level value calculation sectionconfigured to calculate a first corrected level value by adding X% ofthe calculated difference to the first level value; a second correctedlevel value calculation section configured to calculate a secondcorrected level value by subtracting Y% of the calculated differencefrom the second level value; a specifying section configured to specifya first corrected level position and a second corrected level positionat a boundary between the first color area and the second color areaincluded in the acquired image signal, the first corrected levelposition being a position where the level value of the image signal isthe first corrected level value, and the second corrected level positionbeing a position where the level value of the image signal is the secondcorrected level value, as a second corrected level position; a distancecalculation section configured to calculate a distance between thespecified first corrected level position and the specified secondcorrected level position; and a bokeh amount measurement sectionconfigured to measure a bokeh amount of the image at the boundarybetween the first color area and the second color area by multiplyingthe calculated distance by 100/(100−X−Y).
 4. The measurement apparatusaccording to claim 3, further comprising a normalization sectionconfigured to normalize a level value indicated by the acquired imagesignal with reference to a specific range, and use the normalized levelvalue as the level value of the image signal.
 5. A non-transitorycomputer readable recording medium having stored therein a computerprogram for causing a computer to: acquire an image signal by imaging ofan object with a camera, the object including a first color areacomposed of a first color, and a second color area which is composed ofa second color different from the first color and is adjacent to thefirst color area; acquire a first level value that a the level value ofthe image signal in the first color area; acquire a second level valuethat a the level value of the image signal in the second color area;calculate a difference between the first level value and the secondlevel value; calculate a first corrected level value by adding X% of thecalculated difference to the first level value; calculate a secondcorrected level value by subtracting Y% of the calculated differencefrom the second level value; specify a first corrected level positionand a second corrected level position at a boundary between the firstcolor area and the second color area included in the acquired imagesignal, the first corrected level position being a position where thelevel value of the image signal is the first corrected level value, anda second corrected level position being a position where the level valueof the image signal is the second corrected level value, as a secondcorrected level position; calculate a distance between the specifiedfirst corrected level position and the specified second corrected levelposition; and measure a bokeh amount of the image at the boundarybetween the first color area and the second color area by multiplyingthe calculated distance by 100/(100−X−Y).
 6. The non-transitory computerreadable recording medium according to claim 5, further causing thecomputer to normalize a level value indicated by the acquired imagesignal with reference to a specific range, so that the normalized levelvalue is used as the level value of the image signal.
 7. A cameracomprising: an image acquiring section configured to acquire an imagesignal by imaging an object with a camera, the object including a firstcolor area composed of a first color, and a second color area which iscomposed of a second color different from the first color and isadjacent to the first color area; a first level value acquiring sectionconfigured to acquire a first level value that is a level value of theimage signal in the first color area; a second level value acquiringsection configured to acquire a second level value that is a level valueof the image signal in the second color area; a difference calculationsection configured to calculate a difference between the first levelvalue and the second level value; a first corrected level valuecalculation section configured to calculate a first corrected levelvalue by adding X% of the calculated difference to the first levelvalue; a second corrected level value calculation section configured tocalculate a second corrected level value by subtracting Y% of thecalculated difference from the second level value; a specifying sectionconfigured to specify a first corrected level position and a secondcorrected level position at a boundary between the first color area andthe second color area included in the acquired image signal, the firstcorrected level position being a position where the level value of theimage signal is the first corrected level value, and the secondcorrected level position being a position where the level value of theimage signal is the second corrected level value, as a second correctedlevel position; a distance calculation section configured to calculate adistance between the specified first corrected level position and thespecified second corrected level position; and a bokeh amountmeasurement section configured to measure a bokeh amount of the image atthe boundary between the first color area and the second color area bymultiplying the calculated distance by 100/(100−X−Y).
 8. The cameraaccording to claim 7, further comprising a normalization sectionconfigured to normalize a level value indicated by the acquired imagesignal with reference to a specific range, and use the normalized levelvalue as the level value of the image signal.